Rcd As Incomer For Board Isolation

[stuartmcclean]

can a rcd serve as a main incomer switch on a con unit

 

[Evans Electric]

Yes.

 

[Adrian]

yes

 

[Andy™]

yes, but not advisable

 

[ProDave]

May not be advisable for a main CU due to nuisance of everything tripping say when a lamp blows.

But I regularly do this for an economy 7 CU to run a few storage heaters.

 

[Andy™]

a lamp failing should not trip an RCD

 

[Steve3948]

But will especially if lamp facing up and brass lamp holder.

 

[SLIPSHOD & SLAPDASH]

Cant see what a brass lampholder has to do with it, but agree lamps & other items can trip Rcds although they shouldnt.

 

[davetheglitz]

But will especially if lamp facing up and brass lamp holder.

Thanks for that - I've never been able to explain the effect before - but always knew that a lamp will cause a trip.

 

[Steve3948]

Well I've had the filament drop down inside a candle lamp and put RCD out.

 

[davetheglitz]

Cant see what a brass lampholder has to do with it, but agree lamps & other items can trip Rcds although they shouldnt.

Assume when the lamp goes it ionises the tungsten and splits the glass - and the brass lamp holder is earthed?

 

[SLIPSHOD & SLAPDASH]

Well I've had the filament drop down inside a candle lamp and put RCD out.

 Same here, but i cant see what the difference between a brass, plastic or stainless steel lampholder makes ?

 

[Steve3948]

I will go with Dave, as it never happens with lamp facing down.

Brass but not Plastic slips

 

[Andy™]

Well I've had the filament drop down inside a candle lamp and put RCD out.

shouldnt do - the enclosure is all glass, so the only metallic contact with the outside world is the L&N connections. there would need to be some other kind of fault between either L&N to the metallic base, along with an earthed brass holder for an RCD to trip

 

[Steve3948]

shouldnt do - the enclosure is all glass, so the only metallic contact with the outside world is the L&N connections. there would need to be some other kind of fault between either L&N to the metallic base, along with an earthed brass holder for an RCD to trip

I agree, but it does seem to happen on BC lamps, maybe its cheap lamps or the bottom inside the lamps breaks down tracks to the cap when the lamp blows.

 

[OnOff]

can a rcd serve as a main incomer switch on a con unit

If the RCD is a 30mA  one then NOT a good idea as a fault on any circuit could trip everything as the regs highlight. A case of "One out, ALL out!". Not the best idea if a say fault on the immersion heater knocks out the lights too, at night, the customer is elderly etc, etc.

There ARE occasions when you might see a higher rated, say 100mA "time delay" rcd up front as the incomer but it doesn't get away from the fact that circuits may still need 30mA protection elsewhere. Thinking metal cu's on TT earthing system etc.

This, from Hager is a good guide (most makers do a similar guide) also look at the On Site Guide. 

http://download.hager.com/hager.uk/files_download/guides/Consumer%20Unit%20Guide.pdf

If in doubt seek a professional's advice.